parse: merge `fn` syntax + cleanup item parsing
Here we continue the work in https://github.com/rust-lang/rust/pull/67131 in particular to merge the grammars of `fn` items in various positions.
A list of *language level* changes (as sanctioned by the language team in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286 and https://github.com/rust-lang/rust/pull/67131):
- `self` parameters are now *syntactically* allowed as the first parameter irrespective of item context (and in function pointers). Instead, semantic validation (`ast_validation`) is used.
- Syntactically, `fn` items in `extern { ... }` blocks can now have bodies (`fn foo() { ... }` as opposed to `fn foo();`). As above, we use semantic restrictions instead.
- Syntactically, `fn` items in free contexts (directly in a file or a module) can now be without bodies (`fn foo();` as opposed to `fn foo() { ... }`. As above, we use semantic restrictions instead, including for non-ident parameter patterns.
- `const extern fn` feature gating is now done post-expansion such that we do not have conditional compatibilities of function qualifiers *in parsing*.
- The `FnFrontMatter` grammar becomes:
```rust
Extern = "extern" StringLit ;
FnQual = "const"? "async"? "unsafe"? Extern? ;
FnFrontMatter = FnQual "fn" ;
```
That is, all item contexts now *syntactically* allow `const async unsafe extern "C" fn` and use semantic restrictions to rule out combinations previously prevented syntactically. The semantic restrictions include in particular:
- `fn`s in `extern { ... }` can have no qualifiers.
- `const` and `async` cannot be combined.
- To fuse the list-of-items parsing in the 4 contexts that items are allowed, we now must permit inner attributes (`#![attr]`) inside `trait Foo { ... }` definitions. That is, we now allow e.g. `trait Foo { #![attr] }`. This was probably an oversight due to not using a uniform parsing mechanism, which we now do have (`fn parse_item_list`). The semantic support (including e.g. for linting) falls out directly from the attributes infrastructure. To ensure this, we include a test for lints.
Put together, these grammar changes allow us to substantially reduce the complexity of item parsing and its grammar. There are however some other non-language improvements that allow the compression to take place.
A list of *compiler-internal* changes (in particular noting the parser-external data-structure changes):
- We use `enum AllowPlus/RecoverQPath/AllowCVariadic { Yes, No }` in `parser/ty.rs` instead of passing around 3 different `bool`s. I felt this was necessary as it was becoming mentally taxing to track which-is-which.
- `fn visit_trait_item` and `fn visit_impl_item` are merged into `fn visit_assoc_item` which now is passed an `AssocCtxt` to check which one it is.
- We change `FnKind` to:
```rust
pub enum FnKind<'a> {
Fn(FnCtxt, Ident, &'a FnSig, &'a Visibility, Option<&'a Block>),
Closure(&'a FnDecl, &'a Expr),
}
```
with:
```rust
pub enum FnCtxt {
Free,
Foreign,
Assoc(AssocCtxt),
}
```
This is then taken advantage of in tweaking the various semantic restrictions as well as in pretty printing.
- In `ItemKind::Fn`, we change `P<Block>` to `Option<P<Block>>`.
- In `ForeignItemKind::Fn`, we change `P<FnDecl>` to `FnSig` and `P<Block>` to `Option<P<Block>>`.
- We change `ast::{Unsafety, Spanned<Constness>}>` into `enum ast::{Unsafe, Const} { Yes(Span), No }` respectively. This change in formulation allow us to exclude `Span` in the case of `No`, which facilitates parsing. Moreover, we also add a `Span` to `IsAsync` which is renamed to `Async`. The new `Span`s in `Unsafety` and `Async` are then taken advantage of for better diagnostics. A reason this change was made is to have a more uniform and clear naming scheme.
The HIR keeps the structures in AST (with those definitions moved into HIR) for now to avoid regressing perf.
- Various cleanups, bug fixes, and diagnostics improvements are made along the way. It is probably best to understand those via the diffs.
I would recommend reviewing this commit-by-commit with whitespace changes hidden.
r? @estebank @petrochenkov
remove Panic variant from InterpError
The interpreter engine itself does not raise `Panic` errors any more, so remove them from the error enum. Instead, const-prop and const-eval have to do their own handling of panics.
I used the opportunity to refactor the const-eval error handling a bit to use the `MachineStop` variant.
Also, in const-prop I could do some cleanup as now, no more lints are being reported in `use_ecx`. However, I am quite puzzled by why exactly the linting there works the way it does -- the code can certainly be cleaned up more, but I don't know enough of the intent to do that. I left some questions for the most confusing parts, but for now behavior should be unchanged by this PR (so, all that weirdness I am asking about is pre-existing and merely maintained here). Cc @wesleywiser
Fixes https://github.com/rust-lang/rust/issues/66902
r? @oli-obk
parse: unify function front matter parsing
Part of https://github.com/rust-lang/rust/pull/68728.
- `const extern fn` feature gating is now done post-expansion such that we do not have conditional compatibilities of function qualifiers *in parsing*.
- The `FnFrontMatter` grammar becomes:
```rust
Extern = "extern" StringLit ;
FnQual = "const"? "async"? "unsafe"? Extern? ;
FnFrontMatter = FnQual "fn" ;
```
That is, all item contexts now *syntactically* allow `const async unsafe extern "C" fn` and use semantic restrictions to rule out combinations previously prevented syntactically. The semantic restrictions include in particular:
- `fn`s in `extern { ... }` can have no qualifiers.
- `const` and `async` cannot be combined.
- We change `ast::{Unsafety, Spanned<Constness>}>` into `enum ast::{Unsafe, Const} { Yes(Span), No }` respectively. This change in formulation allow us to exclude `Span` in the case of `No`, which facilitates parsing. Moreover, we also add a `Span` to `IsAsync` which is renamed to `Async`. The new `Span`s in `Unsafety` and `Async` are then taken advantage of for better diagnostics. A reason this change was made is to have a more uniform and clear naming scheme.
The HIR keeps the structures in AST (with those definitions moved into HIR) for now to avoid regressing perf.
r? @petrochenkov
bootstrap: Configure cmake when building sanitizer runtimes
Configure cmake before building sanitizer runtimes in similar way it is already
configured elsewhere, to ensure that they are built with expected compiler
flags.
Previously this step has been intentionally omitted since sanitizer runtimes
are built as universal binaries on Darwin targets, which in turn are
unsupported by sccache which is also configured there. To avoid the issue
everything but the compiler launcher is configured.
Helps with #68863.
Micro-optimize the heck out of LEB128 reading and writing.
This commit makes the following writing improvements:
- Removes the unnecessary `write_to_vec` function.
- Reduces the number of conditions per loop from 2 to 1.
- Avoids a mask and a shift on the final byte.
And the following reading improvements:
- Removes an unnecessary type annotation.
- Fixes a dangerous unchecked slice access. Imagine a slice `[0x80]` --
the current code will read past the end of the slice some number of
bytes. The bounds check at the end will subsequently trigger, unless
something bad (like a crash) happens first. The cost of doing bounds
check in the loop body is negligible.
- Avoids a mask on the final byte.
And the following improvements for both reading and writing:
- Changes `for` to `loop` for the loops, avoiding an unnecessary
condition on each iteration. This also removes the need for
`leb128_size`.
All of these changes give significant perf wins, up to 5%.
r? @michaelwoerister
Suggestion when encountering assoc types from hrtb
When encountering E0212, detect whether this is a representable case or
not, i.e. if it's happening on an `fn` or on an ADT. If the former,
provide a structured suggestion, otherwise note that this can't be
represented in Rust.
Fix#69000.
Properly use parent generics for opaque types
Fixes#67844
Previously, opaque types would only get parent generics if they
a return-position-impl-trait (e.g. `fn foo<A>() -> impl MyTrait<A>`).
However, it's possible for opaque types to be nested inside one another:
```rust
trait WithAssoc { type AssocType; }
trait WithParam<A> {}
type Return<A> = impl WithAssoc<AssocType = impl WithParam<A>>;
```
When this occurs, we need to ensure that the nested opaque types
properly inherit generic parameters from their parent opaque type.
This commit fixes the `generics_of` query to take the parent item
into account when determining the generics for an opaque type.
